Structured language vs. statement list

Hi everyone,
I would like to be guided with some wisdom about the differences between Structured Text Language (STL) and Statement list (SL).

My understanding is that STL is more powerful than SL and therefore is more recommended in complexes routines like batch sequencing and execution.

Also I would like to know in your experience if Siemens S7 series can handle STL because I’m sure you can program those in SL.



Best regards, appreciate your feedback.



[font=&quot]Delgado [/font]

Be a bit careful with the acromyns. Siemens uses 'STL' in their documentation to refer to statement list, not structured text.


As far as power, I don't know that structured text is any more or less powerful than statement list. Structured text is often easier deal with for the majority of users. But I don't think it is necessarily more powerful. Given the choice I would use structured text before statement list. But that's just because I'm not a big statement list user and I would feel more comfortable in structured text.

I'm pretty sure that Step7 supports the structured text language. It's probably called something different, though. I have never used it. It wasn't part of the base Step7 package when I was using Siemens stuff.

Keith

Yep, in Siemenese Structured Text is called SCL. S7 SCL conforms to IEC1131-3 Structured Text (ST).

Siemens Statement List (STL) does not conform to IEC1131-3 Instruction List (IL).

STL is the base language for Step 7.

That is LAD, SCL and FBD all translate down to STL.

If you were to program in STL, you could make it more sleek and faster than any of the others, the problam is, outside Europe not many people use STL that often and would find it more difficult to understand.

LAD, SCL and FBD enable methods of programing which more people are comfortable with.

IEC defines IL (Instruction List) and ST (Structured Text). Siemens have STL (non-IEC) and SCL accordingly. STL gives you full possibilities because this is must closer to Siemens CPU commands - like ASM for PC. STL like IL is accumulator-oriented. SCL is high level Pascal-style language.
This means SCL (not STL) is much easier to realize complex tasks. And is faster in program developing. But STL is faster in execution than other languages because code is more optimal. And some Siemens stuffs (like work with address registers) can be realized in STL only. Everyone who wants to know Siemens well must know STL.

I've used structured text (i.e. Siemens SCL) and have transferred functions and function blocks to/from the Beckhoff Twincat environment. It was surprisingly easy.